Early Downward Trends in Neurodevelopmental Disorders Following Removal of Thimerosal-Containing Vaccines
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Early Downward Trends in Neurodevelopmental Disorders Following Removal of Thimerosal-Containing Vaccines David A. Geier, B.A. Thimerosal is an ethylmercury-containing compound (49.6% Mark R. Geier, M.D., Ph.D. mercury by weight) that was historically added to many vaccines at the preservative level (0.005% to 0.01%). The U.S. Centers for Disease Control and Prevention (CDC), from the late 1980s ABSTRACT through the 1990s, expanded the number of doses of TCVs to be administered to U.S. infants. To five doses of diptheria-tetanus- Contemporaneously with the epidemic rise in neuro- developmental disorders (NDs), first observed in the United States whole-cell-pertussis (DTP) vaccine were added three doses of during the 1990s, the childhood immunization schedule was hepatitis B (Hep b) vaccine and four of Haemophilus influenzae expanded by the U.S. Centers for Disease Control and Prevention type b (Hib) vaccine. Additionally, the CDC began recommending (CDC) to include several additional thimerosal-containing vaccines three doses of influenza vaccine for certain infant populations. An (TCVs). On July 7, 1999, a joint recommendation was made by the infant who received all of these vaccines on schedule could have American Academy of Pediatrics (AAP) and the U.S. Public Health received as much as 200 micrograms (µg) of mercury during the Service (PHS) to remove thimerosal from vaccines. A two-phase first 6 months of life.14 study was undertaken to evaluate trends in diagnosis of new NDs In response to theoretical concerns about the cumulative doses entered into the Vaccine Adverse Event Reporting System of mercury from TCVs, theAAPand the U.S. Public Health Service (VAERS) and the California Department of Developmental Services (PHS) issued a joint statement on July 7, 1999, calling for the (CDDS) databases on a reporting quarter basis, from 1994 through removal of thimerosal from all vaccines.14 It has been estimated that 2005. Significant increasing trends in newly diagnosed NDs were the last thimerosal-containing Hep b, diphtheria-tetanus-acellular- observed in both databases 1994 through mid-2002. Significant pertussis (DTaP) and Hib vaccines were manufactured in 2000- decreasing trends in newly diagnosed NDs were observed in both 14 databases from mid-2002 through 2005. The results indicate that 2001 and expired at the end of 2002 (or early 2003). Table 1 the trends in newly diagnosed NDs correspond directly to the summarizes significant historical dates in the use of pediatric TCVs expansion and subsequent contraction of the cumulative mercury in the United States. dose to which children were exposed from TCVs through the U.S. Considering all significant environmental exposures to immunization schedule. mercury, such as through breast milk, TCVs represent almost 50% of the total mercury dose some infants received.15 The 187.5 µg of Background mercury through TCVs plus the average of 164 µg from breast milk during the first 6 months exceeded the methylmercury safety In 2004, the Department of Health and Human Services and guidelines established by the U.S. Environmental Protection the American Academy of Pediatrics (AAP) issued an Autism Agency (EPA), Health Canada, the World Health Organization A.L.A.R.M., stating that 1 in 166 children currently have an (WHO), the Agency for Toxic Substances Disease Registry 15 autistic disorder, and 1 in 6 children have a developmental and/or (ATSDR), and the U.S. Food and Drug Administration (FDA). behavioral disorder. Autism, once rare, is now more prevalent With no additional exposure from any source, these doses also 1 exceeded the methylmercury guidelines for the first year of life set than childhood cancer, diabetes, and Down syndrome. Epidemic 15 trends in neurodevelopmental disorders (NDs) were first by all of these agencies except the FDA. observed in the United States during the 1990s,1-8 and cannot be Despite its removal from many childhood vaccines, thimerosal explained by immigration, changed diagnostic criteria, or is still routinely added to some formulations of influenza vaccine administered to U.S. infants, as well as to several other vaccines improved identification.1, 6-8 (e.g. tetanus-diphtheria and monovalent tetanus) administered to Autism is an ND characterized by impairments in social older children and adults. In 2004, the Institute of Medicine (IOM) relatedness and communication, repetitive behaviors, and 1 of the U.S. NationalAcademy of Sciences (NAS) retreated from the stereotypic abnormal movements. While genetic factors are stated 1999 goal of theAAPand the PHS to remove thimerosal from important in the pathogenesis of autistic disorders, a role for U.S. vaccines as soon as possible.16 Furthermore, many nations still environmental factors has received considerable attention. add thimerosal to many of their pediatric vaccines, and WHO and Exposure to mercury has previously been shown to cause several vaccine manufacturers still advocate the continued use of immune, sensory, neurological, motor, and behavioral thimerosal in pediatric vaccines. As a result, assessing the safety of dysfunctions similar to traits defining or associated with autistic TCVs is a matter of significant importance. disorders, and with similarities in neuroanatomy, neuro- Examinations of the VaccineAdverse Event Reporting System transmitters, and biochemistry.9-12 Furthermore, recent research that (VAERS), the U.S. Department of Education, and the Vaccine codes children’s communicative, social, affective, repetitive Safety Datalink (VSD) databases showed significant links between behaviors, and toy play from videotapes of the toddlers’ first and exposure to TCVs and NDs.17-23 Specifically, data from VAERS second birthday parties demonstrates that the regression associated showed that additional doses of mercury from thimerosal- with autistic disorders clearly manifests between the ages of 12 and containing DTaP in comparison to thimerosal-free DTaP 24 months,13 concurrent with the exposure to thimerosal-containing (administered in the late 1990s), and additional doses of childhood vaccines (TCVs). thimerosal-containing DTP and Hib in comparison to diphtheria- 8 Journal of American Physicians and Surgeons Volume 11 Number 1 Spring 2006 Table 1. Significant Dates Regarding the Use of Thimerosal in U.S. Pediatric Vaccines Date Significant Events Middle 1980s Thimerosal is present in virtually all whole-cell diphtheria-tetanus-whole-cell-pertussis (DTP) vaccines administered to children four times, starting at age 2 mon, during the first 18 mon of life (maximum of 25 µg Hg/dose). Maximum Hg exposure in 18 mon: 100 µg. Late 1980s Thimerosal-containingHaemophilus influenzae type b (Hib) vaccine is administered to children at age 18 mon (maximum of 25 µg Hg/dose). Maximum Hg exposure in 18 mon: 125 µg. Early 1990s Four doses of thimerosal-containing Hib are recommended within 18 months, starting at age 2 mon (maximum of 25 µg Hg/dose). Maximum Hg exposure in 18 mon: 200 µg. Early 1990s Three doses of thimerosal-containing hepatitis B (Hep b) vaccine are recommended within the first 6 mon, starting on the day of birth (maximum of 12.5 µg Hg/dose). Maximum Hg exposure in 18 mon: 237.5 µg. Middle 1990s Some DTP and Hib vaccines are combined to produce DTPH vaccine, which has only 25 µg of mercury per immunization, reducing mercury levels of exposure for some children, but is rapidly replaced by diphtheria-tetanus-acellular-pertussis (DTaP) vaccines beginning in 1996 (DTaPvaccine is almost exclusively produced separately from Hib vaccine). 1996-1997 GlaxoSmithKline introduces a new thimerosal-free DTaP vaccine (Infarix) that contains 2-phenoxethanol as a preservative. Aventis Pasteur introduces a new Hib vaccine (ActHIB) that contains no preservative. Late 1990s Three doses of thimerosal-containing influenza vaccine are increasingly recommended for administration to children during the first 18 mon, starting at age 6 mon (12.5 µg Hg/dose). Maximum Hg exposure: 200 µg in first 6 mon and 275 µg in first 18 mon. July 7, 1999 AAP and PHS request removal of thimerosal from all pediatric vaccines as rapidly as possible, and AAP suggests delaying Hep b vaccine until after age 6 mon for children born to hepatitis B negative mothers. August 27, 1999** Thimerosal-free Recombivax HB (Merck) is licensed by the FDA. March 28, 2000 Thimerosal-free Engerix-B (GlaxoSmithKline) is licensed by the FDA. March 7, 2001 Thimerosal-free Tripedia (Aventis Pasteur) is licensed by the FDA. Late 2002/ CDC and FDA claim that the last remaining doses of thimerosal-containing DTaP, Hep b, or Hib vaccines are administered to U.S. Early 2003 children. ** Thimerosal-containing formulations continued to be distributed/administered following FDA licensing of thimerosal-free formulations. tetanus-pertussis-Haemophilus influenzae type b (DTPH) vaccines adverse events following vaccination are required by law to be (ad-ministered in the early to mid-1990s), were associated with a reported to this database. The VAERS Working Group of the CDC significant 2- to 8-fold increase in risk of NDs, depending upon the has previously reported that less than 5% of the reports come from symptoms or outcomes examined. The one other U.S. parents. The VAERS Working Group and the FDA analyze and epidemiological study that has examined the relationship between publish epidemiologic studies based upon analyses of VAERS. TCVs and NDs, by Verstaeten et al. from the CDC, initially found a They note that VAERS is simple to use, flexible by design, and significant